The invention relates to a cleaning composition for removing reactive polyurethane (PUR) hot melt adhesive compositions from production and processing devices, machines and equipment, in particular application apparatus and the like.
Known cleaning composition are formed by substances which do not react chemically with the hot melt adhesive, instead only mixing with the adhesive which remains in and is to be removed from, the apparatus to be cleaned, and only diluting and displacing said adhesive.
A known cleaning composition of this kind consists of a mixture of an ethyl vinyl acetate (EVA) polymer with a resin component. The EVA polymer does not mix well with conventional PUR hot melt adhesives. Moreover, the hot melt adhesive--due to its still reactive NCO functionality--continues to react in the mixture to give cross-linked products which are very difficult to remove since they are unmeltable and essentially insoluble in the compositions, and therefore form deposits.
As an alternative, compositions have recently been discussed (unpublished information) which are obtained by adding an exact amount (no excess) of a monofunctional alcohol to a reactive hot melt adhesive, whereby the reactive NCO groups of the PUR hot melt adhesive which are still present are completely stoichiometrically saturated by the hydroxyl groups of the monofunctional alcohol. The mass thus formed, which in total is not reactive (anymore), approximately corresponds to the known cleaning composition on EVA basis in its application properties, and specifically does not react with the PUR adhesive in the apparatus during cleaning. These compounds, therefore, when used to remove unreacted adhesive, would also exhibit the disadvantage that no neutralization of the reactive NCO groups of the PUR hot melt adhesive is achieved so that in this case, too, the PUR hot melt adhesive would continue to react even during cleaning. The PUR hot melt adhesive again would react to give unmeltable and insoluble end products which are very difficult to remove.